Lemme see if I've got this straight. The Senate and SCOTUS have passed a law and upheld that law, respectively, which requires TikTok to be divested from its current owners to operate in the USA or be banned. However, Biden - the Executive branch of the government and therefore the part in charge of enforcing these things - declined to enforce simply because it was pointless. The ban was going to come into force one day before the Executive changed hands. Nevertheless TikTok complied. Later today, they decided to reverse that decision on assurances from the President Elect that he would allow a delay in enforcement. Whilst that Executive Order for a delay could be challenged by the Senate, it's within reasonable limits and not unheard of, so unlikely. TikTok gets to operate for a while longer. Technically, being operative since the ban came into force and BEFORE the new President's EO is signed means they're violating the law. But they're not going to get prosecuted for that, just for one day.
So far, so good, if a little crazy.
But what's really going on here? Trump started this whole thing, as others have pointed out. So why the leniency? Here's my guess. It's because, as he has already stated, he sees an opportunity for a buck. As it stands, TT in the USA is worthless. But if he gives it a short delay, there's time to find a buyer. A USA company can come in for a distressed purchase at a knock down value. Trump isn't interested in MAGA. He's interested in MMGA - Make Me Great Again. Only in it for what he can get out of it. He's just gaming the system for a win.